1. A variable, pointer, or index. Its fluctuation reveals the variations in key elements of a system. The position and trend of the indicator in relation to reference points or values indicate the present state and dynamics of the system. Indicators provide a bridge between objectives and action; 2. Signals of processes, inputs, outputs, effects, results, outcomes, impacts, etc. , that enable such phenomena to be judged or measured. Both qualitative and quantitative indicators are needed for management learning, policy review, monitoring, and evaluation; 3. In biology, an organism, species, or community whose characteristics show the presence of specific environmental conditions, good or bad.